"Because at that point in time no one knew what it was and if we weren't the source of contamination we were likely to be blamed for the contamination as well."
Just four of the 120 staff fell ill - indicating their innocence early on - but testing still had to be done.
"At the mushroom farm we make compost and as part of that compost process we use chicken manure, and chickens can carry campo and high levels of E.coli."
Mr Whittaker says the farm has an effluent pond which is managed by the Hawke's Bay Regional Council.
"That has high levels of E.coli so there was a natural assumption that it could be from chicken."
The farm has private water bores and isn't on the town supply.
But, being the weekend, no laboratories were open and their water couldn't be tested.
"Monday morning the first thing, as soon as the laboratories opened, we had water samples in there for testing and at that point was when we called the regional council and said you better come in, our doors are open, you've got unfettered access to the farm to have a look because if it is us we need to know and if it's not us you need to tell us it's not us."
Tests were cleared.
Council testing confirmed the contamination was from sheep faeces.
"It really disassociated the link between what we do in our manufacturing process to what you would classify as normal farming practice and what you would see in the stream so, as I say, that was a big turning point for us in terms of trying to break that link."
"But fair to say all the damage had already been done in the media. I think long term, yeah, there is some damage that could go on for many years."
Mr Whittaker says there is no blueprint for a business to deal with an outbreak of this magnitude.
The first stage of an inquiry into what caused the contamination has just finished.
The panel identified several failings by the Hastings District Council, Hawke's Bay Regional Council and drinking water assessors.
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